What are studio apartments?

Can someone please elaborate? I am hunting some list of homes to live in SG.

Commonly, a fancy estate agent way to describe a tiny flat where you sleep on a sofa bed and the kitchen is part of the living room.
The only other room is a shower toilet, with a door if you're lucky.

Edit - Imagine a hotel room, and the quality varies about as much.

The difference between studio apartment and 1+1 units in Singapore is that you don't have a common area in studio apartment Nor has a separate kitchen area (may be at best case a very small kitchen space attached to your studio bed room).

Please note that studio and one-room apartments are very rare in Singapore and usually cost as much or more than two-room units.

@beppi I disagree about it costs more. Currently, I am looking for a place to live in SG and 1BHK are rare but I found a lot of reasonable Studio rooms near East Coast and Pearl Park if compared to Two Bedroom which is costing double.

If you have suggestions to give, you're most welcome.